#define _CRT_SECURE_NO_WARNINGS 1

#include <vector>
#include <queue>
using namespace std;

class Solution {
    int dx[4] = { 0,0,1,-1 };
    int dy[4] = { 1,-1,0,0 };
public:
    vector<vector<int>> highestPeak(vector<vector<int>>& isWater) {
        int m = isWater.size();
        int n = isWater[0].size();
        vector<vector<int>> ret(m, vector<int>(n, -1));
        queue<pair<int, int>> q;
        for (int i = 0; i < m; ++i)
            for (int j = 0; j < n; ++j)
            {
                if (isWater[i][j] == 1)
                {
                    ret[i][j] = 0;
                    q.push({ i,j });
                }
            }
        while (q.size())
        {
            int sz = q.size();
            while (sz--)
            {
                auto [a, b] = q.front();
                q.pop();
                for (int k = 0; k < 4; ++k)
                {
                    int x = a + dx[k], y = b + dy[k];
                    if (x >= 0 && x < m && y >= 0 && y < n && ret[x][y] == -1)
                    {
                        ret[x][y] = ret[a][b] + 1;
                        q.push({ x,y });;
                    }
                }
            }
        }
        return ret;
    }
};